1. Field of the Invention
This invention relates to a process for modifying the surface of glass. In particular the invention relates to a process in which metal ions are induced to migrate into a hot glass surface from a molten metal body in contact with the glass surface, and to surface-modified glass produced by that process.
2. Description of the Prior Art
In one such process the surfaces of a hot ribbon of glass are contacted with electrically isolated bodies of molten electrically conductive material and a controlled electric current is passed through the glass between the molten bodies. Ions migrate from the anodic molten body into the glass surface and modify the surface characteristics of the glass. Metal ions introduced into the glass surface in this way may remain in ionic form or may be reduced to the metal by exposing the hot glass surface to a reducing atmosphere.
A metal locating member may be used to locate a molten body in position on the glass surface, from which body migration of ions into the glass surface is induced. The locating member may be a metal bar which is mounted above and transversely of a moving ribbon of the glass being treated, the molten body being located on the upper surface of the ribbon by clinging to the underface of the locating member.
Migration of metal ions from a molten metal body into the glass may be induced by regulating the concentration of oxygen in the molten body, for example, by contacting the molten body with a controlled amount of oxidising gas.
A molten alloy body may be used as the source of metal ions which migrate into the glass and the relative proportions of the two metals which migrate may be controlled. This control may be achieved by regulating the temperature of the glass and the voltage applied to bring about migration.
It has now been found that, when two or more metals are simultaneously introduced into the glass from a molten alloy body in contact with the glass, it is particularly advantageous to locate the molten metal body in contact with the glass surface by using a locating member having a locating surface comprising the metals which enter the glass from the molten body.